[igt-dev] [PATCH i-g-t v3] lib/igt_debugfs: explicitly wait for first crc in igt_pipe_crc_start

[Mahesh Kumar <mahesh1.kumar@intel.com>]

Now crc framework does not wait for first CRC during open, User need
to wait for crc if he wants so.
This patch make changes in igt_pipe_crc_start to make sure we wait
until first crc available after open to keep the tests behaviour same.
Without this if driver is skipping few initial crcs there will be
mismatch in expected and actual number of crcs returned by crc
framework.

Changes Since V1:
 - poll instead of read_one_crc (Maarten)
Changes Since V2:
 - poll without timeout, we already have igt_timeout (Maarten)

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
---
 lib/igt_debugfs.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
index f3196f43..4de6b247 100644
--- a/lib/igt_debugfs.c
+++ b/lib/igt_debugfs.c
@@ -35,6 +35,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <i915_drm.h>
+#include <poll.h>
 
 #include "drmtest.h"
 #include "igt_aux.h"
@@ -748,6 +749,7 @@ static void read_one_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out)
 void igt_pipe_crc_start(igt_pipe_crc_t *pipe_crc)
 {
 	const char *src = pipe_crc_source_name(pipe_crc->source);
+	struct pollfd pfd;
 	char buf[32];
 
 	/* Stop first just to make sure we don't have lingering state left. */
@@ -757,11 +759,16 @@ void igt_pipe_crc_start(igt_pipe_crc_t *pipe_crc)
 
 	sprintf(buf, "crtc-%d/crc/data", pipe_crc->pipe);
 
-	igt_set_timeout(10, "Opening crc fd, which waits for first CRC.");
+	igt_set_timeout(10, "Opening crc fd, and poll for first CRC.");
 	pipe_crc->crc_fd = openat(pipe_crc->dir, buf, pipe_crc->flags);
+	igt_assert(pipe_crc->crc_fd != -1);
+
+	pfd.fd = pipe_crc->crc_fd;
+	pfd.events = POLLIN;
+	poll(&pfd, 1, -1);
+
 	igt_reset_timeout();
 
-	igt_assert(pipe_crc->crc_fd != -1);
 	errno = 0;
 }
 
-- 
2.16.2

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